Rheostat



J. C. SNELL RHEOSTAT Feb. 17. `1925- v 1,526,441

Filed June 4, 1923 Fgl. M a

Willi 2 27 Patented F eb. 17, 1925.

UNITEDI STATES PATENT JAMES C. SNELL, 0F OAK PARK, ILLINOIS, ASSIGNOR T0 PRENIIER ELECTRIC COM- IPANY, 0F CHICAGO, ILLINOIS,

A CORPORATION 0F ILLINOIS.

RHEOSTAT;

Application led June 4,

To all whom it may concern.' y

Be it known that I, JAMES C. SNELL, a citizen of the United States,.and a resident of Oak Park, in the county of Cook and State of Illinois, have invented certainl new1 and useful Improvements in Rheostats, of which the Afollowing is a full,`clear, and ex' act description.

The invention relates to rheostats and more particularly to those adapted for radio service and its object is to provide. an improved device in which provision is made for quick or coarse and fine adjustment'for corresponding variations in the resistance in the circuit.

The invention consists in the several novel features hereinafter set forth and more particularly defined by claims at the conclusion hereof.

In the drawings: Fig. 1 is a plan of a device embodying the invention. Fig. 2 is a rear elevation. Fig 3 `is asection on line 3-3 of Fig. 1. Fig. 4 is a diagram of the electrical connections. Fig. 5 isa detailed perspective of the rheostat frame.

The invention is exemplified in a rheostat comprisinga semi-circular or arched core 6 of insulating material; a bracket or frame 7 between the ends ofthe core and provided with laterally extending lugs 8 which are riveted to theco-re and with holes 10 for screws whereby the frame may be supported in any suitable manner; a ribbon or wire resistance coil 11 wound on said core and having one of its ends electrically connected to a terminal strip 12 to which one of the conductors 9 of the circuitis connected. The other conductor-9a is connected to a terminal strip 13 which is riveted to bracket 7 which forms apart of the electrical circuit. A sleeve 15 is pivotally mounted in frame 7. A conductor or switch-arm 16 has its hun 1.7 secured by a screw 18 to sleeve 15 and is adapted to travel over one side of the coil 11 to. include more or less of the convolutions thereof in the circuitv between conductors 9 and 9, the arm servin as a conductor between bracket 7 and said coil. A handle 18 is fixed by a screw 19 to sleeve 15, so that arm 16 may be rotatively adjusted over any part of the resistance coil.

A shunt coil 27 'is wound on a core 28 of insulating material which is separated from the core 6 and coil 11. One end of coil 27 is connected to a terminal strip 29 which is thirty to vforty units.

1923. Serial No. 643,202.

also connected to circuit-conductor 9. The 'resistance fof coil 27 is at least greater than the resistance of coil 11.' For example, if the coil 11 has a resistance of ten units, the shuntcoil 27 would have a resistance of from Coils 11 and 27 are connected in parallel to conductor 9. A shaft 2O extends through sleeve 15 and carries at its rear end a conductor arm 22, the hub 23 of which is fixed to vsaid shaft by a screw 24. The outer end of arm 22 engages one side of the coil 27 and is rotatable so that it maybe shifted to include more or less of the coil 27 in the shunt circuit between the conductors 9, 9a through coil 27, arm 22, and frame 7. Arms 16 and 22 are slightly resilient to provide good contacts against the coils respectively. A handle 01' finger-piece 25 for turning arm 22 is secured by screw 26 to the front end of shaft 20. By means of handles 18 and 25, the conductor arms are separately adjusted. A stop 36 is provided to limit the sweep of arm 22 so that the minimum resistance included in the shunt circuit will be at least as great as the maximum resistance in Ithe main circuit through coil 11. This also prevents reversal of current through the coils to the contacts. Coil 27 and arm 22 exempli a shunt resistance in the circuit which i variable for the purpose of a finer adjustment of the fiow of 4current between conductors 9 and 9 Arms 16 and 22 constitute separately movable contacts which are connected to conductor 9a and are adapted to include in parallel more or less of the resistance coils in the circuit between conductors 9 and 9a. i

The operation will be as follows: Norjmally, arms 16 and 22 will be disposed advmay be adjusted to effect a finer adjustment of the resistance in the circuit. By shifting arm 22 over coil 27, a shunt circuit will be established` between conductor 9 through coil .27, arm 22 and :trame 7 With resistance that varies accordin to the position of arm 22. Under the resistance heretofore given by Way of example, the movement of arm 22v will eect a very tine variation of resistance in the circuit because the variation is made by increasing or decreasing the convolutions of the high resistance coil. As a result, an extremely'. fine variation of the resistance may be eected by variation of the resistance includedl in the shunt circuit. vents arm 22 from being shifted so that the resistance of the shunt coil will be less than the maximum resistance of the main coil.

The invention exemplifies an improved rheostat, in which provision is made fora quick or coarse adjustment and'for an extremely iine variation by means of a shunt circuit.

The invention is not to'i'be understood as restricted to the details set forth, since these may be modified Withinthe scope oi the appended claims, Without departing from the spirit and scope of the invention.

' Having thus described the invention, what 'I claim as new and desire to secure by Iletters Patent, is: o

l. In a rheostat, the combination of a plurality of resistance coils connected in parallel to one conductor of acircuit, and separately operable contacts connected to the other conductor, engaging the coi s respectivel and movable to include more or less of t e coils in parallel in the circuit between said conductors.

2. In a rheostat, the combination of a plurality of coils of relatively high and low re-A sistance and connected inaparallel to one conductor of va circuit, and separately operable contacts connected to the other conductor, engaging the coils respectively, and movable to include more or less of the coils in parallel in the circuit between said conductors. v

o 3. In a rheostat, the combination ofja plurality of resistance coils connected in paral-v Stop pre-A neeaeei lel to one conductor of a circuit, a plurality of separately operable contacts for the coils 'respectivelyv and-connected to the other -conductor, and separately movable to include more or less of the coils in parallel in the circuit, and means to limit the movement of one of the contacts to. prevent reversal ofl current through the coils.

4. lIn a rheostat, the combination of a plu.u

rality of coils of relatively high and 10W ref sistance and connected in parallel to one conductor of a circuit, a plurality of scparately operable contacts for the coils respectively and connected to the other conductor, and vseparately movable to include more or less-of the coils'in parallelA in the circuit, and stop-means to limit the movement of the contact Which engages the high current tatably supported, the coils bein also supported on said frame, said frame eing elec trically connected to the other conductor.

6. In a rheos'tat, the combination of ax plurality of resistance coils connected in parallel to one conductor of a circuit, separately operable contacts for the coilsrespectively, and movable to include more or less'of the coils in lparallel in the circuit, a frame in which both of the contacts are electrically connected and in which Athey are rotatably supported, the coils being ixedly supported on said frame, and a stop on the fra-nie to limit movement or one of the contacts to prevent reversal of current through the coils.

Shiued at Chicago, Illinois, this 4th day of a ,1923.

' I -Tl S C. SNELL.I 

